Method for preventing abnormality during wireless charging

ABSTRACT

Disclosed is a control method of a wireless power transmitter, including transmitting power to a plurality of wireless power receivers based on a first power value required by a first wireless power receiver from among the plurality of wireless power receivers, selecting, before reaching a threshold condition in which a system error occurs in the wireless power transmitter, a second wireless power receiver from among the plurality of wireless power receivers, and in response to the second wireless power receiver being selected, transmitting power to the plurality of wireless power receivers based on a second power value required by the second wireless power receiver, wherein the system error comprises at least one of an over-temperature error, an over-current error, and an over-voltage error.

PRIORITY

This is a Continuation Application of U.S. patent application Ser. No.15/720,740, filed with the U.S. Patent and Trademark Office on Sep. 29,2017, which is a Continuation Application of U.S. patent applicationSer. No. 14/627,710, filed with the U.S. Patent and Trademark Office onFeb. 20, 2015, now U.S. Pat. No. 9,787,365, issued on Oct. 10, 2017, andclaims priority under 35 U.S.C. § 119(a) to a Korean Patent Applicationfiled on Feb. 20, 2014 in the Korean Intellectual Property Office andassigned Serial No. 10-2014-0019941, the content of each of which isincorporated herein by reference.

BACKGROUND 1. Field of the Invention

The present invention relates generally to wireless charging, and moreparticularly, to a method for preventing an abnormality during wirelesscharging.

2. Description of the Related Art

In view of their nature, mobile terminals such as portable phones andPersonal Digital Assistants (PDAs) are powered by rechargeablebatteries. To charge the batteries, the mobile terminals applyelectrical energy to the batteries via chargers. Typically, the chargerand the battery each have an exterior contact terminal and thus areelectrically connected to each other by contacting their contactterminals.

This contact-based charging scheme faces the problem of vulnerability ofcontact terminals to contamination by foreign materials and theresulting unreliable battery charging because the contact terminalsprotrude outward. Moreover, if the contact terminals are exposed tomoisture, the batteries may not be charged properly.

To address the above problem, wireless charging or contactless charginghas recently been developed and applied to many electronic devices.

Such wireless charging is based on wireless power transmission andreception. For example, once a portable phone is placed on a chargingpad without being connected to an additional charging connector, itsbattery is automatically charged. Among wirelessly charged products,wireless electric toothbrushes or wireless electric shavers are wellknown. Wireless charging offers the benefits of increased waterproofnessdue to wireless charging of electronic products and enhanced portabilitydue to no need for a wired charger for electronic devices. Further, itis expected that wireless charging will be more developed for electricvehicles.

There are three wireless charging schemes: electromagnetic inductionusing coils, resonance-based wireless charging, and Radio Frequency(RF)/microwave radiation based on the conversion of electrical energy tomicrowaves.

To date, the electromagnetic induction-based wireless charging schemehas been most popular. However, considering recent successfulexperiments in wireless power transmission over microwaves at a distanceof tens of meters in Korea and other overseas countries, it isforeseeable that every electronic product will be charged wirelessly atany time in any place in the near future.

Electromagnetic induction-based power transmission refers to powertransfer between primary and secondary coils. When a magnet movesthrough a coil, current is induced. Based on this principle, atransmitter creates a magnetic field and a receiver produces energy bycurrent induced by a change in the magnetic field. This phenomenon iscalled magnetic induction and power transmission based on magneticinduction is highly efficient in energy transfer.

A resonance-based wireless charging system has achieved wireless energytransfer from a charger at a distance of a few meters based on theresonance-based power transmission principle by the Coupled Mode Theory.The resonated electromagnetic waves carried electric energy instead ofsound. The resonant electrical energy is directly transferred only inthe presence of a device having the same resonant frequency, while theunused electrical energy is reabsorbed into the electromagnetic fieldrather than being dispersed into the air. Thus, the resonant electricalenergy does not affect machines or human beings, as compared to otherelectronic waves.

Wireless charging is an active research area. Thus, there is a need fordeveloping a standard regarding wireless charging priority, detection ofa wireless power transmitter/receiver, communication frequency selectionbetween a wireless power transmitter and a wireless power receiver,wireless power control, selection of a matching circuit, and allocationof a communication time to each wireless power receiver in a singlecharging cycle. Particularly, there exists a need for developingstandards for a configuration and procedure that allow a wireless powerreceiver to select a wireless power transmitter from which to receivewireless power.

A single wireless power transmitter can supply charging power to aplurality of wireless power receivers. Because the plurality of wirelesspower receivers are different in terms of characteristics, states, andtypes, various algorithms may be performed to determine transmissionpower of the wireless power transmitter.

If an abnormality occurs in at least one wireless power receiver duringwireless charging with transmission power determined according to aspecific algorithm in the wireless power transmitter, the wirelesscharging may fail.

For example, a wireless power transmitter or a wireless power receivermay be placed in an error situation such as over voltage, over current,or over temperature due to a specific algorithm or some defect in thewireless power receiver.

If the error situation is not self-corrected, the wireless powertransmitter may enter a latch fault mode in which it is powered off andprompts a user to reset it, in order to protect the wireless powertransmitter or each wireless power receiver which is being charged.

However, if the wireless power transmitter enters the latch fault mode,the user is required to solve the problem, which is not favorable interms of User eXperience (UX).

Accordingly, there is a need for a self-correcting method for preventingan abnormal situation from developing to an extreme in a system.

SUMMARY

The present invention has been made to address at least theabove-mentioned problems and/or disadvantages, and to provide at leastthe advantages described below.

An aspect of the present invention provides a control method of awireless power transmitter, including transmitting power to a pluralityof wireless power receivers based on a first power value required by afirst wireless power receiver from among the plurality of wireless powerreceivers, selecting, before reaching a threshold condition in which asystem error occurs in the wireless power transmitter, a second wirelesspower receiver from among the plurality of wireless power receivers, andin response to the second wireless power receiver being selected,transmitting power to the plurality of wireless power receivers based ona second power value required by the second wireless power receiver,wherein the system error comprises at least one of an over-temperatureerror, an over-current error, and an over-voltage error.

Another aspect of the present invention provides a wireless powertransmitter for wirelessly charging a plurality of wireless powerreceivers, including a power transmitter configured to wirelesslytransmit power to the plurality of wireless power receivers based on afirst power value required by a first wireless power receiver, acommunication unit configured to transmit a signal to the plurality ofwireless power receivers, and a controller configured to select, beforereaching a threshold condition in which a system error occurs in thewireless power transmitter, a second wireless power receiver from amongthe plurality of wireless power receivers, and in response to the secondwireless power receiver being selected, control the power transmitter totransmit power to the plurality of wireless power receivers based on asecond power value required by the second wireless power receiver,wherein the system error comprises at least one of an over-temperatureerror, an over-current error, and an over-voltage error.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will be more apparent from the following description, taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating an overall operation of awireless charging system;

FIG. 2 is a block diagram illustrating a wireless power transmitter anda wireless power receiver according to an embodiment of the presentinvention;

FIG. 3 is a block diagram illustrating a wireless power transmitter anda wireless power receiver according to an embodiment of the presentinvention;

FIG. 4 is a diagram illustrating a signal flow for operations of awireless power transmitter and a wireless power receiver according to anembodiment of the present invention;

FIG. 5 is a flowchart illustrating a signal flow for operations of awireless power transmitter and a wireless power receiver according toanother embodiment of the present invention;

FIG. 6 is a graph illustrating amounts of power applied by a wirelesspower transmitter with respect to a time axis;

FIG. 7 is a flowchart illustrating a method for controlling a wirelesspower transmitter according to an embodiment of the present invention;

FIG. 8 is a graph illustrating amounts of power applied by a wirelesspower transmitter with respect to a time axis according to FIG. 7;

FIG. 9 is a flowchart illustrating a method for controlling a wirelesspower transmitter according to an embodiment of the present invention;

FIG. 10 is a graph illustrating amounts of power supplied by a wirelesspower transmitter with respect to a time axis according to FIG. 9;

FIG. 11 is a block diagram illustrating a wireless power transmitter anda wireless power receiver in a Stand Alone (SA) mode according to anembodiment of the present invention;

FIG. 12 is a flowchart illustrating an operation for preventing anabnormality during wireless charging according to an embodiment of thepresent invention;

FIG. 13 is a flowchart illustrating an operation for preventing anabnormality during wireless charging according to an embodiment of thepresent invention;

FIG. 14 is a flowchart illustrating an operation for preventing anabnormality during wireless charging according to an embodiment of thepresent invention; and

FIG. 15 is a flowchart illustrating an operation for preventing anabnormality during wireless charging according to an embodiment of thepresent invention

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of embodiments ofthe present invention as defined by the appended claims and theirequivalents. It includes details to assist in that understanding butthese are to be regarded as mere examples. Accordingly, those ofordinary skill in the art will recognize that various changes andmodifications of the embodiments of the present invention describedherein can be made without departing from the scope and spirit of thepresent invention. In addition, descriptions of well-known functions andconstructions are omitted for clarity and conciseness. Throughout thedrawings, like reference numerals will be understood to refer to likeparts, components, and structures.

The terms and words used in the following description and claims are notlimited to their dictionary meanings, but are merely used to enable aclear and consistent understanding of the present invention.Accordingly, it should be apparent to those skilled in the art that thefollowing description of embodiments of the present invention isprovided for illustration purposes only and not for the purpose oflimiting the present invention as defined by the appended claims andtheir equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

The term “substantially” refers to a recited characteristic, parameter,or value that need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

A description is first given of the concept of a wireless chargingsystem applicable to embodiments of the present invention with referenceto FIGS. 1 to 11, followed by a detailed description of methods forpreventing an abnormality during wireless charging according to variousembodiments of the present invention with reference to FIGS. 12 to 15.

FIG. 1 is a block diagram illustrating an overall operation of awireless charging system.

Referring to FIG. 1, the wireless charging system includes a wirelesspower transmitter (or Power Transmitting Unit (PTU)) 100 and one or morewireless power receivers (or Power Receiving Units (PRUs)) 110-1, 110-2,. . . , and 110-n.

The wireless power transmitter 100 wirelessly transmits power 1-1, 1-2,. . . , and 1-n, respectively, to the wireless power receivers 110-1,110-2, . . . , and 110-n. More specifically, the wireless powertransmitter 100 may wirelessly transmit the power 1-1, 1-2, . . . , and1-n only to wireless power receivers that have been authenticated in apredetermined authentication procedure.

The wireless power transmitter 100 establishes electrical connections tothe wireless power receivers 110-1, 110-2, . . . , and 110-n. Forexample, the wireless power transmitter 100 transmits wireless power inthe form of electromagnetic waves to the wireless power receivers 110-1,110-2, . . . , and 110-n.

The wireless power transmitter 100 conducts bi-directional communicationwith the wireless power receivers 110-1, 110-2, . . . , and 110-n. Thewireless power transmitter 100 and the wireless power receivers 110-1,110-2, . . . , and 110-n process or transmit/receive packets 2-1, 2-2, .. . , and 2-n configured in predetermined frames. The frames will bedescribed below in greater detail. A wireless power receiver 110-1,110-2, . . . , 110-n may be configured as a mobile communicationterminal, a Personal Digital Assistant (PDA), a Personal MultimediaPlayer (PMP), a smartphone, or the like.

The wireless power transmitter 100 applies power wirelessly to theplurality of wireless power receivers 110-1, 110-2, . . . , and 110-n.For example, the wireless power transmitter 100 transmits power to theplurality of wireless power receivers 110-1, 110-2, . . . , and 110-n byresonance. If the wireless power transmitter 100 adopts the resonancescheme, the distance between the wireless power transmitter 100 and thewireless power receivers 110-1, 110-2, . . . , and 110-n may be 30 m orsmaller. If the wireless power transmitter 100 adopts an electromagneticinduction scheme, the distance between the wireless power transmitter100 and the wireless power receivers 110-1, 110-2, . . . , and 110-n maybe 10 cm or smaller.

The wireless power receivers 110-1, 110-2, . . . , and 110-n receivewireless power from the wireless power transmitter 100 and charge theirinternal batteries. Further, the wireless power receivers 110-1, 110-2,. . . , and 110-n transmit to the wireless power transmitter 100 asignal requesting wireless power transmission, information required forwireless power reception, wireless power receiver state information, orcontrol information for the wireless power transmitter 100. Informationof the transmitted signal is described below in greater detail.

Each of the wireless power receivers 110-1, 110-2, . . . , and 110-nalso transmits a message indicating its charged state to the wirelesspower transmitter 100.

The wireless power transmitter 100 includes a display means such as adisplay and displays the state of each wireless power receiver 110-1,110-2, . . . , 110-n based on the messages received from the wirelesspower receivers 110-1, 110-2, . . . , and 110-n. Further, the wirelesspower transmitter 100 displays a time when it is expected that each ofthe wireless power receivers 110-1, 110-2, . . . , and 110-n will becompletely charged.

The wireless power transmitter 100 transmits a control signal fordisabling a wireless charging function to the wireless power receivers110-1, 110-2, . . . , and 110-n. Upon receipt of the control signal fordisabling the wireless charging function from the wireless powertransmitter 100, a wireless power receiver 110-1, 110-2, . . . , 110-ndisables the wireless charging function.

FIG. 2 is a block diagram illustrating a wireless power transmitter 200and a wireless power receiver 250 according to an embodiment of thepresent invention.

Referring to FIG. 2, the wireless power transmitter 200 includes atleast one of a power transmission unit 211, a controller 212, acommunication unit 213, a display unit 214, and a storage unit 215.

The power transmission unit 211 supplies power required for the wirelesspower transmitter 200 and wirelessly supplies power to the wirelesspower receiver 250. The power transmission unit 211 supplies power inthe form of Alternate Current (AC) waveforms or by converting power inDirect Current (DC) waveforms to power in AC waveforms by means of aninverter. The power transmission unit 211 may be implemented as abuilt-in battery. Alternatively, the power transmission units 211 may beimplemented as a power reception interface so as to receive power fromexternally and supply the power to other components. It will beunderstood by those skilled in the art that as far as it can supplypower in AC waveforms, any means may be used as the power transmissionunit 211.

The controller 212 provides overall control to the wireless powertransmitter 200. The controller 212 controls the overall operation ofthe wireless power transmitter 200 using an algorithm, a program, or anapplication required for a control operation, read from the storage unit215. The controller 212 may be configured as a Central Processing Unit(CPU), a microprocessor, or a mini computer.

The communication unit 213 communicates with the wireless power receiver250 in a predetermined communication scheme. The communication unit 213receives power information from the wireless power receiver 250. Thepower information includes information about at least one of thecapacity, residual battery amount, use amount, battery capacity, andbattery proportion of the wireless power receiver 250.

Further, the communication unit 213 transmits a charging functioncontrol signal for controlling the charging function of the wirelesspower receiver 250. The charging function control signal is a controlsignal that enables or disables the charging function by controlling apower reception unit 251 of the wireless power receiver 250.Alternatively, the power information includes information aboutinsertion of a wired charging terminal, transition from a Stand Alone(SA) mode to a Non-Stand Alone (NSA) mode, error state release, and thelike, as described below in detail.

In addition, the charging function control signal includes informationrelated to power control or a power adjust command to cope with anoccurrence of an abnormality according to an embodiment of the presentinvention.

The communication unit 213 may receive a signal from another wirelesspower transmitter as well as the wireless power receiver 250.

The controller 212 displays a state of the wireless power receiver 250on the display unit 214 based on a message received from the wirelesspower receiver 250 via the communication unit 213. Further, thecontroller 212 displays a time by which the wireless power receiver 250is expected to be completely charged, on the display unit 214.

As illustrated in FIG. 2, the wireless power receiver 250 includes atleast one of a power reception unit 251, a controller 252, acommunication unit 253, a display unit 258, and a storage unit 259.

The power reception unit 251 receives power wirelessly from the wirelesspower transmitter 200. The power reception unit 251 receives power inthe form of AC waveforms from the wireless power transmitter 200.

The controller 252 provides overall control to the wireless powerreceiver 250. The controller 252 controls the overall operation of thewireless power receiver 250 using an algorithm, a program, or anapplication required for a control operation, read from the storage unit259. The controller 252 may be configured as a CPU, a microprocessor, ora mini computer.

The communication unit 253 communicates with the wireless powertransmitter 200 in a predetermined communication scheme. Thecommunication unit 253 transmits power information to the wireless powertransmitter 200. The power information includes information about atleast one of the capacity, residual battery amount, use amount, batterycapacity, and battery proportion of the wireless power receiver 250.

Further, the communication unit 253 transmits a charging functioncontrol signal for controlling the charging function of the wirelesspower receiver 250. The charging function control signal is a controlsignal that enables or disables the charging function by controlling thepower reception unit 251 of the wireless power receiver 250.Alternatively, the power information includes information aboutinsertion of a wired charging terminal, transition from the SA mode tothe NSA mode, error state release, and the like, as described below indetail.

Further, the charging function control signal includes informationrelated to power control or a power adjust command to cope with anoccurrence of an abnormality according to an embodiment of the presentinvention.

The controller 252 displays a state of the wireless power receiver 250on the display unit 258. Further, the controller 252 displays a time bywhich the wireless power receiver 250 is expected to be completelycharged, on the display unit 258.

FIG. 3 is a block diagram illustrating the wireless power transmitter200 and the wireless power receiver 250 according to an embodiment ofthe present invention.

Referring to FIG. 3, the wireless power transmitter 200 includes atleast one of a Transmission (Tx) resonator 211 a, the controller 212(for example, a Micro Controller Unit (MCU)), the communication unit 213(for example, an out-of-band signaling unit), a matching unit 216, adriver (e.g. a power supply) 217, a Power Amplifier (PA) 218, and asensing unit 219. The wireless power receiver 250 includes at least oneof a Reception (Rx) resonator 251 a, the controller 252, thecommunication unit 253, a rectifier 254, a DC/DC converter 255, aswitching unit 256, and a loading unit 257.

The driver 217 outputs DC power having a predetermined voltage value.The voltage value of the DC power output from the driver 217 iscontrolled by the controller 212.

A DC current output from the driver 217 is applied to the PA 218. The PA218 amplifies the DC current with a predetermined gain. Further, the PA218 converts DC power to AC power based on a signal received from thecontroller 212. Therefore, the PA 218 outputs AC power.

The matching unit 216 performs impedance matching. For example, thematching unit 216 controls an impedance viewed from the matching unit216 so that its output power has high efficiency or high power. Thesensing unit 219 senses a load variation of the wireless power receiver250 via the Tx resonator 211 a or the PA 218 and provides the sensingresult to the controller 212.

The matching unit 216 adjusts impedance under control of the controller212. The matching unit 216 includes at least one of a coil and acapacitor. The controller 212 controls a connection state to at leastone of the coil and the capacitor and thus may perform impedancematching accordingly.

The Tx resonator 211 a transmits input AC power to the Rx resonator 251a. The Tx resonator 211 a and the Rx resonator 251 a are configured asresonant circuits having the same resonant frequency. For example, theresonant frequency may be determined to be 6.78 MHz.

The communication unit 213 communicates with the communication unit 253of the wireless power receiver 250, for example, bi-directionally at 2.4GHz (by Wireless Fidelity (WiFi), ZigBee, or Bluetooth (BT)/BluetoothLow Energy (BLE)).

The Rx resonator 251 a receives power for charging.

The rectifier 254 rectifies wireless power received from the Rxresonator 251 a to DC power. For example, the rectifier 254 may beconfigured as a bridge diode. The DC/DC converter 255 converts therectified power with a predetermined gain. For example, the DC/DCconverter 255 converts the rectified power so that the voltage of itsoutput may be 5V. A minimum voltage value and a maximum voltage valuethat may be applied to the input of the DC/DC converter 255 may bepreset.

The switching unit 256 connects the DC/DC converter 255 to the loadingunit 257. The switching unit 256 is kept in an ON or OFF state under thecontrol of the controller 252. The switching unit 256 may be omitted. Ifthe switching unit 256 is in the ON state, the loading unit 257 storesthe converted power received from the DC/DC converter 255.

FIG. 4 is a diagram illustrating a signal flow for operations of awireless power transmitter 400 and a wireless power receiver 450according to an embodiment of the present invention.

Referring to FIG. 4, the wireless power transmitter 400 is powered ON,in step S401. Upon power-on, the wireless power transmitter 400configures an environment, in step S402.

The wireless power transmitter 400 enters a power save mode, in stepS403. In the power save mode, the wireless power transmitter 400 appliesdifferent types of power beacons for detection, with their respectiveperiods, which will be described below in greater detail with referenceto FIG. 6. For example, the wireless power transmitter 400 transmitspower beacons 404 and 405 for detection (for example, short beacons orlong beacons) and the power beacons 404 and 405 may have different powervalues. One or both of the power beacons 404 and 405 for detection mayhave sufficient power to drive the communication unit of the wirelesspower receiver 450. For example, the wireless power receiver 450communicates with the wireless power transmitter 400 by driving itscommunication unit by means of one or both of the power beacons 404 and405 for detection. This state may be referred to as a null state.

The wireless power transmitter 400 detects a load variation caused bydisposition of the wireless power receiver 450. The wireless powertransmitter 400 enters a low power mode, in step S408. The low powermode is described below in greater detail with reference to FIG. 6. Thewireless power receiver 450 drives the communication unit with powerreceived from the wireless power transmitter 400, in step S409.

The wireless power receiver 450 transmits a PTU searching signal to thewireless power transmitter 400, in step S410. The wireless powerreceiver 450 may transmit the PTU searching signal by a BLE-basedAdvertisement (AD) signal. The wireless power receiver 450 may transmitthe PTU searching signal periodically until it receives a responsesignal from the wireless power transmitter 400 or a predetermined timeperiod lapses.

Upon receipt of the PTU searching signal from the wireless powerreceiver 450, the wireless power transmitter 400 transmits a PRUresponse signal, in step S411. The PRU response signal establishes aconnection between the wireless power transmitter 400 and the wirelesspower receiver 450.

The wireless power receiver 450 transmits a PRU static signal, in stepS412. The PRU static signal indicates a state of the wireless powerreceiver 450 and requests joining in a wireless power network managed bythe wireless power transmitter 400.

The wireless power transmitter 400 transmits a PTU static signal, instep S413. The PTU static signal indicates capabilities of the wirelesspower transmitter 400.

Once the wireless power transmitter 400 and the wireless power receiver450 transmit and receive the PRU static signal and the PTU staticsignal, the wireless power receiver 450 transmits a PRU dynamic signalperiodically, in steps S414 and S415. The PRU dynamic signal includes atleast one parameter measured by the wireless power receiver 450. Forexample, the PRU dynamic signal may include information about a voltageat the output of a rectifier of the wireless power receiver 450. Thestate of the wireless power receiver 450 may be referred to as a bootstate, in step S407.

The wireless power transmitter 400 enters a power transfer mode, in stepS416. The wireless power transmitter 400 transmits a PRU control signalcommanding charging to the wireless power receiver 450, in step S417. Inthe power transfer mode, the wireless power transmitter 400 transmitscharging power.

The PRU control signal transmitted by the wireless power transmitter 400includes information that enables/disables charging of the wirelesspower receiver 450 and permission information. The PRU control signalmay be transmitted each time a charged state is changed. For example,the PRU control signal may be transmitted every 250 ms or uponoccurrence of a parameter change. The PRU control signal may beconfigured to be transmitted within a predetermined threshold time, forexample, within 1 second, even though no parameter is changed.

The wireless power receiver 450 changes a setting according to the PRUcontrol signal and transmits a PRU dynamic signal to report a state ofthe wireless power receiver 450, in step S418 and S419. The PRU dynamicsignal transmitted by the wireless power receiver 450 includesinformation about at least one of a voltage, a current, a wireless powerreceiver state, and a temperature. The state of the wireless powerreceiver 450 may be referred to as an ON state.

The PRU dynamic signal may have the following data structure illustratedin Table 1 below.

TABLE 1 Field Octets Description Use Units Optional fields 1 Defineswhich optional fields Mandatory are populated V_(RECT) 2 Voltage atdiode output Mandatory mV I_(RECT) 2 Current at diode output MandatorymA V_(OUT) 2 Voltage at charge/battery port Optional mV I_(OUT) 2Current at charge/battery port Optional mA Temperature 1 Temperature ofPRU Optional Deg C. from −40 C. V_(RECT) _(—) _(MIN) _(—) _(DYN) 2V_(RECT) _(—) _(LOW) _(—) _(LIMIT) Optional mV (dynamic value) V_(RECT)_(—) _(SET) _(—) _(DYN) 2 Desired V_(RECT) Optional mV (dynamic value)V_(RECT) _(—) _(HIGH) _(—) _(DYN) 2 V_(RECT) _(—) _(HIGH) _(—) _(LIMIT)Optional mV (dynamic value) PRU alert 1 Warnings Mandatory Bit field RFU3 Undefined

Referring to Table 1, the PRU dynamic signal includes one or morefields. The fields provide optional field information, information abouta voltage at the output of the rectifier of the wireless power receiver,information about a current at the output of the rectifier of thewireless power receiver, information about a voltage at the output ofthe DC/DC converter of the wireless power receiver, information about acurrent at the output of the DC/DC converter of the wireless powerreceiver, temperature information, information about a minimum voltagevalue VRECT_MIN_DYN at the output of the rectifier of the wireless powerreceiver, information about an optimum voltage value VRECT_SET_DYN atthe output of the rectifier of the wireless power receiver, informationabout a maximum voltage value VRECT_HIGH_DYN at the output of therectifier of the wireless power receiver, and warning information. ThePRU dynamic signal may include at least one of the above fields.

For example, at least one voltage set value that has been determinedaccording to a charging situation (for example, the information about aminimum voltage value VRECT_MIN_DYN at the output of the rectifier ofthe wireless power receiver, the information about an optimum voltagevalue VRECT_SET_DYN at the output of the rectifier of the wireless powerreceiver, and the information about a maximum voltage valueVRECT_HIGH_DYN at the output of the rectifier of the wireless powerreceiver) may be transmitted in the at least one field of the PRUdynamic signal. Upon receipt of the PRU dynamic signal, the wirelesspower transmitter may adjust a wireless charging voltage to betransmitted to each wireless power receiver based on the voltage valueset in the PRU dynamic signal.

Among the fields, PRU Alert may be configured in the data structureillustrated in Table 2.

TABLE 2 7 6 5 4 3 2 1 0 Overvoltage Overcurrent Overtemp Charge TATransition restart RFU complete detect request

Referring to Table 2, PRU Alert may include a bit for a restart request,a bit for a transition, and a bit for Travel Adapter (TA) detect. The TAdetect bit indicates that a wireless power receiver has been connectedto a wired charging terminal in the wireless power transmitter thatprovides wireless charging. The Transition bit indicates to the wirelesspower transmitter that a communication Integrated Circuit (IC) of thewireless power receiver is reset before the wireless power receivertransitions from the SA mode to the NSA mode. Finally, the restartrequest bit indicates that the wireless power transmitter is ready toresume charging of the wireless power receiver when the wireless powertransmitter that has discontinued charging by reducing transmissionpower due to over current or over temperature returns to a normal state.

PRU Alert may also be configured in the data structure illustrated inTable 3 below.

TABLE 3 7 6 5 4 3 2 1 0 PRU PRU PRU PRU Self Charge Wired Mode Modeover- over- over- Protection Complete Charger Transition Transitionvoltage current temperature Detect Bit 1 Bit 0

Referring to Table 3, PRU Alert includes the fields of over voltage,over temperature, PRU Self Protection, Charge Complete, Wired ChargerDetect, and Mode Transition. If the over voltage field is set to “1”,this implies that the voltage Vrect of the wireless power receiver hasexceeded an over voltage limit. The over current and over temperaturefields may be set in the same manner as the over voltage field. PRU SelfProtection refers to the wireless power receiver protecting itself bydirectly reducing power affecting a load. In this case, the wirelesspower transmitter does not need to change a charged state.

According to an embodiment of the present invention, bits for ModeTransition are set to a value indicating the duration of a modetransition to the wireless power transmitter. The Mode Transition bitsmay be configured as illustrated in Table 4.

TABLE 4 Value(Bit) Mode Transition Bit Description 00 No Mode Transition01 2 s Mode Transition time limit 10 3 s Mode Transition time limit 11 6s Mode Transition time limit

Referring to Table 4, if the Mode Transition bits are set to “00”, thisindicates no mode transition. If the Mode Transition bits are set to“01”, this indicates that a time limit for completion of a modetransition is 2 seconds. If the Mode Transition bits are set to “10”,this indicates that the time limit for completion of a mode transitionis 3 seconds. If the Mode. Transition bits are set to “11”, thisindicates that the time limit for completion of a mode transition is 6seconds.

For example, if a mode transition takes 3 seconds or less, the ModeTransition bits may be set to “10”. Before starting a mode transition,the wireless power receiver ensures that no impedance shift will occurduring the mode transition by changing an input impedance setting tomatch a 1.1 W power draw. Accordingly, the wireless power transmitteradjusts a power ITX_COIL for the wireless power receiver according tothis setting and thus maintains the power ITX_COIL for the wirelesspower receiver during the mode transition.

Therefore, once a mode transition duration is set by the Mode Transitionbits, the wireless power transmitter maintains the power ITX_COIL forthe wireless power receiver during the mode transition duration, forexample, for 3 seconds. In other words, even though the wireless powertransmitter does not receive a response from the wireless power receiverfor 3 seconds, the wireless power transmitter maintains a connection tothe wireless power receiver. However, after the mode transition durationlapses, the wireless power transmitter ends the power transmission,considering that the wireless power receiver is a rogue object.

The wireless power receiver 450 senses generation of an error. Thewireless power receiver 450 transmits a warning signal to the wirelesspower transmitter 400, in step S420. The warning signal may betransmitted by a PRU dynamic signal or an alert signal. For example, thewireless power receiver 450 may transmit the PRU Alert field illustratedin Table 1 to indicate an error state to the wireless power transmitter400. Alternatively, the wireless power receiver 450 may transmit astand-alone warning signal indicating an error state to the wirelesspower transmitter 400. Upon receipt of the warning signal, the wirelesspower transmitter 400 enters a latch fault mode, in step S422. Thewireless power receiver 450 enters a null state, in step S423.

FIG. 5 is a flowchart illustrating a signal flow for operations of awireless power transmitter and a wireless power receiver according to anembodiment of the present invention. The control method of FIG. 5 isdescribed below in detail with reference to FIG. 6.

FIG. 6 is a graph illustrating amounts of power applied by the wirelesspower transmitter with respect to a time axis.

Referring to FIG. 5, the wireless power transmitter starts to operate,in step S501. Further, the wireless power transmitter rests an initialsetting, in step S503 and enters the power save mode, in step S505. Thewireless power transmitter applies different types of power havingdifferent power amounts to a power transmitter in the power save mode.For example, the wireless power transmitter may apply second detectionpower 601 and 602 and third detection power 611 to 615 to the powertransmitter in FIG. 6. The wireless power transmitter may apply thesecond detection power 601 and 602 periodically with a second period.When the wireless power transmitter supplies the second detection power601 and 602, the second detection power 601 and 602 may last for asecond time duration. The wireless power transmitter may apply the thirddetection power 611 to 615 periodically with a third period. When thewireless power transmitter supplies the third detection power 611 to615, the third detection power 611 to 615 may last for a third timeduration. The third detection power 611 to 615 may have the same powervalue, or different power values as illustrated in FIG. 6.

After outputting the third detection power 611, the wireless powertransmitter outputs the third detection power 612 having the same poweramount. If the wireless power transmitter outputs third detection powerhaving the same amount as described above, the third detection power mayhave a power amount sufficient to detect the smallest wireless powerreceiver, for example, a wireless power receiver of Category 1.

In contrast, after outputting the third detection power 611, thewireless power transmitter may output the third detection power 612having a different power amount. If the wireless power transmitteroutputs different amounts of third detection power as described above,the respective power amounts of the third detection power may besufficient to detect wireless power receivers of Category 1 to Category5. For example, the third detection power 611 may have a power amountsufficient to detect a wireless power receiver of Category 5, the thirddetection power 612 may have a power amount sufficient to detect awireless power receiver of Category 3, and the third detection power 613may have a power amount sufficient to detect a wireless power receiverof Category 1.

The second detection power 601 and 602 may drive the wireless powerreceiver. More specifically, the second detection power 601 and 602 mayhave a power amount sufficient to drive the controller and/or thecommunication unit of the wireless power receiver.

The wireless power transmitter may apply the second detection power 601and 602 and the third detection power 611 to 615 respectively with thesecond and third periods to the wireless power receiver. If the wirelesspower receiver is placed on the wireless power transmitter, impedanceviewed from the wireless power transmitter may be changed. The wirelesspower transmitter may detect an impedance shift during application ofthe second detection power 601 and 602 and the third detection power 611to 615. For example, the wireless power transmitter may detect animpedance shift during application of the third detection power 615.Therefore, the wireless power transmitter may detect an object, in stepS507. If no object is detected, in step S507, e.g. NO, the wirelesspower transmitter is kept in the power save mode in which it appliesdifferent types of power periodically, in step S505.

If the wireless power transmitter detects an object due to an impedanceshift, in step S507, e.g. YES, the wireless power transmitter enters thelow power mode. In the low power mode, the wireless power transmitterapplies a driving power having a power amount sufficient to drive thecontroller and the communication unit of the wireless power receiver.For example, the wireless power transmitter applies driving power 620 tothe power transmitter in FIG. 6. The wireless power receiver receivesthe driving power 620 and drives the controller and/or the communicationunit with the driving power 620. The wireless power receivercommunicates with the wireless power transmitter with the driving power620 in a predetermined communication scheme. For example, the wirelesspower receiver may transmit and receive data required for authenticationand may join a wireless power network managed by the wireless powertransmitter based on the data. However, if a rogue object is placedinstead of a wireless power receiver, data transmission and receptionare not performed. Therefore, the wireless power transmitter determineswhether the object is a rogue object, in step S511. For example, if thewireless power transmitter fails to receive a response from the objectfor a predetermined time, the wireless power transmitter determines theobject to be a rogue object.

If the wireless power transmitter determines the object to be a rogueobject, in step S511, e.g. YES, the wireless power transmitter entersthe latch fault mode, in step S513. In contrast, if the wireless powertransmitter determines that the object is not a rogue object, in stepS511, e.g., NO, the wireless power transmitter may proceeds to a joiningoperation, in step S519. For example, the wireless power transmitter mayapply first power 631 to 634 periodically with a first period in FIG. 6.The wireless power transmitter may detect an impedance shift duringapplication of the first power. For example, if the rogue object isremoved, in step S515, e.g. YES, the wireless power transmitter detectsan impedance shift and thus determines that the rogue object has beenremoved. In contrast, if the rogue object is not removed, in step S515,e.g. NO, the wireless power transmitter does not detect an impedanceshift and thus determines that the rogue object has not been removed. Ifthe rogue object has not been removed, the wireless power transmitternotifies a user that the wireless power transmitter is currently in anerror state by performing at least one of illuminating a lamp oroutputting a warning sound. Accordingly, the wireless power transmitterincludes an output unit for illuminating a lamp and/or outputting awarning sound.

If determining that the rogue object has not been removed, in step S515,e.g. NO, the wireless power transmitter maintains the latch fault mode,in step S513. In contrast, if the rogue object has been removed, in stepS515, e.g. YES, the wireless power transmitter reenters the power savemode, in step S517. For example, the wireless power transmitter mayapply second power 651 and 652 and third power 661 to 665 in FIG. 6.

As described above, if a rogue object is placed on the wireless powertransmitter, instead of a wireless power receiver, the wireless powertransmitter enters the latch fault mode. Further, the wireless powertransmitter determines whether the rogue object has been removed basedon an impedance shift that occurs according to power applied in thelatch fault mode. That is, a condition of entry to the latch fault modeis the presence of a rogue object in the embodiment illustrated in FIGS.5 and 6. Besides the presence of a rogue object, the wireless powertransmitter may have many other conditions for entry to the latch faultmode. For example, the wireless power transmitter may be cross-connectedto a mounted wireless power receiver. In this case, the wireless powertransmitter also enters the latch fault mode.

When the wireless power transmitter is cross-connected to a wirelesspower receiver, the wireless power transmitter must return to an initialstate and the wireless power receiver should be removed. The wirelesspower transmitter may set cross connection of a wireless power receiverplaced on another wireless power transmitter, that is, joining of awireless power receiver placed on another wireless power transmitter ina wireless power network managed by the wireless power transmitter, as acondition for entry to the latch fault mode. An operation of a wirelesspower transmitter upon occurrence of an error such as cross connectionis described below with reference to FIG. 7.

FIG. 7 is a flowchart illustrating a method for controlling a wirelesspower transmitter according to an embodiment of the present invention.The control method of FIG. 7 is described below in detail with referenceto FIG. 8.

FIG. 8 is a graph illustrating amounts of power supplied by the wirelesspower transmitter with respect to a time axis according to theembodiment of the present invention illustrated in FIG. 7.

Referring to FIG. 7, the wireless power transmitter starts to operate,in step S701. Further, the wireless power transmitter may reset aninitial setting, in step S703, and may enter the power save mode, instep S705. The wireless power transmitter may apply different types ofpower having different power amounts to the power transmitter in thepower save mode. For example, the wireless power transmitter may applysecond detection power 801 and 802 and third detection power 811 to 815to the power transmitter in FIG. 8. The wireless power transmitter mayapply the second detection power 801 and 802 periodically with a secondperiod. When the wireless power transmitter applies the second detectionpower 801 and 802, the second detection power 801 and 802 lasts for asecond time duration. The wireless power transmitter may apply the thirddetection power 811 to 815 periodically with a third period. When thewireless power transmitter applies the third detection power 811 to 815,the third detection power 811 to 815 lasts for a third time duration.The third detection power 811 to 815 may have the same power value, ordifferent power values as illustrated in FIG. 8.

The second detection power 801 and 802 may drive the wireless powerreceiver. More specifically, the second detection power 801 and 802 mayhave a power amount sufficient to drive the controller and/or thecommunication unit of the wireless power receiver.

The wireless power transmitter may apply the second detection power 801and 802 and the third detection power 811 to 815 respectively with thesecond and third periods to the wireless power receiver. If the wirelesspower receiver is placed on the wireless power transmitter, impedanceviewed from the wireless power transmitter may be changed. The wirelesspower transmitter may detect an impedance shift during application ofthe second detection power 801 and 802 and the third detection power 811to 815. For example, the wireless power transmitter may detect animpedance shift during application of the third detection power 815.Therefore, the wireless power transmitter detects an object, in stepS707. If no object is detected, in step S707, e.g. NO, the wirelesspower transmitter is kept in the power save mode in which it appliesdifferent types of power periodically, in step S705.

If the wireless power transmitter detects an object due to an impedanceshift, in step S707, e.g. YES, the wireless power transmitter enters thelow power mode, in step S709. In the low power mode, the wireless powertransmitter applies a driving power having a power amount sufficient todrive the controller and/or the communication unit of the wireless powerreceiver. For example, the wireless power transmitter applies drivingpower 820 to the power transmitter in FIG. 8. The wireless powerreceiver receives the driving power 820 and drives the controller and/orthe communication unit with the driving power 820. The wireless powerreceiver communicates with the wireless power transmitter with thedriving power 820 in a predetermined communication scheme. For example,the wireless power receiver transmits and receives data required forauthentication and joins a wireless power network managed by thewireless power transmitter based on the data.

Subsequently, the wireless power transmitter enters the power transfermode in which it transmits charging power, in step S711. For example,the wireless power transmitter applies charging power 821 and thecharging power 821 is transmitted to the wireless power receiver, asillustrated in FIG. 8.

In the power transfer mode, the wireless power transmitter determineswhether an error has occurred. The error may be the presence of a rogueobject, cross connection, over voltage, over current, or overtemperature. The wireless power transmitter includes a sensing unit formeasuring over voltage, over current, or over temperature. For example,the wireless power transmitter measures a voltage or current at areference point and determines that a measured voltage or currentexceeding a threshold satisfies an over voltage or over currentcondition. Alternatively, the wireless power transmitter includes atemperature sensor, and the temperature sensor measures a temperature ata reference point of the wireless power transmitter. If the temperatureat the reference point exceeds a threshold, the wireless powertransmitter determines that an over temperature condition is satisfied.

If the wireless power transmitter determines an over voltage, overcurrent, or over temperature state according to a measured voltage,current, or temperature value, the wireless power transmitter preventsover voltage, over current, or over temperature by decreasing wirelesscharging power by a predetermined value. If the voltage value of thedecreased wireless charging power is below a set minimum value (forexample, the minimum voltage value VRECT_MIN_DYN at the output of therectifier of the wireless power receiver), wireless charging isdiscontinued and thus a voltage set value is re-adjusted according to anembodiment of the present invention.

While continued presence of a rogue object on the wireless powertransmitter is shown as an error in the embodiment of the presentinvention illustrated in FIG. 8, the error is not limited to thecontinued presence of a rogue object. Thus, it will be readilyunderstood to those skilled in the art that the wireless powertransmitter may operate in a similar manner regarding the presence of arogue object, cross connection, over voltage, over current, and overtemperature.

If no error occurs, in step S713, e.g. NO, the wireless powertransmitter maintains the power transfer mode, in step S711. Incontrast, if an error occurs, in step S713, e.g. YES, the wireless powertransmitter enters the latch fault mode, in step S715. For example, thewireless power transmitter applies first power 831 to 835 as illustratedin FIG. 8. Further, the wireless power transmitter outputs an errornotification including at least one of lamp illumination or a warningsound during the latch fault mode. If determining that the rogue objector the wireless power receiver has not been removed, in step S717, e.g.NO, the wireless power transmitter maintains the latch fault mode, instep S715. In contrast, if determining that the rogue object or thewireless power receiver has been removed, in step S717, e.g. YES, thewireless power transmitter reenters the power save mode, in step S719.For example, the wireless power transmitter applies second power 851 and852 and third power 861 to 865 in FIG. 8.

An operation of a wireless power transmitter upon occurrence of an errorduring transmission of charging power has been described above. Below, adescription is provided of an operation of the wireless powertransmitter, when a plurality of wireless power receivers placed on thewireless power transmitter receive charging power from the wirelesspower transmitter.

FIG. 9 is a flowchart illustrating a method for controlling a wirelesspower transmitter according to an embodiment of the present invention.The control method of FIG. 9 is described below in detail with referenceto FIG. 9.

FIG. 10 is a graph illustrating amounts of power applied by the wirelesspower transmitter with respect to a time axis according to theembodiment of the present invention illustrated in FIG. 9.

Referring to FIG. 9, the wireless power transmitter transmits chargingpower to a first wireless power receiver, in step S901. The wirelesspower transmitter also transmits charging power to a second wirelesspower receiver, in step S905. More specifically, the wireless powertransmitter applies the sum of charging power required for the firstwireless power receiver and charging power required for the secondwireless power receiver to power receivers of the first and secondwireless power receivers.

An embodiment of steps S901 to S905 is illustrated in FIG. 10. Forexample, the wireless power transmitter maintains the power save mode inwhich the wireless power applies second detection power 1001 and 1002and third detection power 1011 to 1015. Subsequently, the wireless powertransmitter detects the first wireless power receiver and enters the lowpower mode in which the wireless power transmitter maintains detectionpower 1020. Then, the wireless power transmitter enters the powertransfer mode in which the wireless power transmitter applies firstcharging power 1030. The wireless power transmitter detects the secondwireless power receiver and allows the second wireless power receiver tojoin the wireless power network. In addition, the wireless powertransmitter applies second charging power 1040 being the sum of chargingpower required for the first wireless power receiver and charging powerrequired for the second wireless power receiver.

Referring to FIG. 9, while transmitting charging power to both the firstand second wireless power receivers, in step S905, the wireless powertransmitter detects an error, in step S907. As described above, theerror may be due to the presence of a rogue object, cross connection,over voltage, over current, or over temperature. If no error occurs, instep S907, e.g., NO, the wireless power transmitter continues to applysecond charging power 1040.

In contrast, if an error occurs, in step S907, e.g. YES, the wirelesspower transmitter enters the latch fault mode, in step S909. Forexample, the wireless power transmitter applies first power 1051 to 1055with a first period as illustrated in FIG. 10. The wireless powertransmitter determines whether both the first and second wireless powerreceivers have been removed, in step S911. For example, the wirelesspower transmitter detects an impedance shift while applying the firstpower 1051 to 1055. The wireless power transmitter determines whetherboth the first and second wireless power receivers have been removed bychecking whether an impedance has returned to an initial value.

If determining that both the first and second wireless power receivershave been removed, in step S911, e.g. YES, the wireless powertransmitter enters the power save mode, in step S913. For example, thewireless power transmitter applies second detection power 1061 and 1062and third detection power 1071 to 1075 respectively with second andthird periods, as illustrated in FIG. 10.

As described above, even though the wireless power transmitter appliescharging power to a plurality of wireless power receivers, upon anoccurrence of an error, the wireless power transmitter may readilydetermine whether a wireless power receiver or a rogue object has beenremoved.

FIG. 11 is a block diagram of a wireless power transmitter and awireless power receiver in the SA mode according to an embodiment of thepresent invention.

Referring to FIG. 11, a wireless power transmitter 1100 includes acommunication unit 1110, a PA 1120, and a resonator 1130. A wirelesspower receiver 1150 includes a communication unit 1151, an ApplicationProcessor (AP) 1152, a Power Management Integrated Circuit (PMIC) 1153,a Wireless Power Integrated Circuit (WPIC) 1154, a resonator 1155, anInterface Power Management IC (IFPM) 1157, a TA 1158, and a battery1159.

The communication unit 1110 of the wireless power transmitter 1100 maybe configured as a WiFi/BT combo IC and may communicate with thecommunication unit 1151 in the wireless power receiver 1150 in apredetermined communication scheme, for example, in BLE. For example,the communication unit 1151 of the wireless power receiver 1150 maytransmit a PRU dynamic signal having the afore-described data structureillustrated in Table 1 to the communication unit 1110 of the wirelesspower transmitter 1100. As described above, the PRU dynamic signal mayinclude at least one of voltage information, current information, andtemperature information about the wireless power receiver 1150.

An output power value from the PA 1120 may be adjusted based on thereceived PRU dynamic signal. For example, if over voltage, over current,or over temperature is applied to the wireless power receiver 1150, apower value output from the PA 1120 may be decreased. If the voltage orcurrent of the wireless power receiver 1150 is below a predeterminedvalue, the power value output from the PA 1120 may be increased.

Charging power from the resonator 1130 of the wireless power transmitter1100 is transmitted wirelessly to the resonator 1155 of the wirelesspower receiver 1150.

The WPIC 1154 rectifies the charging power received from the resonator1155 and performs DC/DC conversion on the rectified charging power. TheWPIC 1154 drives the communication unit 1151 or charges the battery 1159with the converted power.

A wired charging terminal may be inserted into the TA 1158. A wiredcharging terminal such as a 30-pin connector or a Universal Serial Bus(USB) connector may be inserted into the TA 1158. The TA 1158 mayreceive power from an external power source and charge the battery 1159with the received power.

The IFPM 1157 processes the power received from the wired chargingterminal and outputs the processed power to the battery 1159 and thePMIC 1153.

The PMIC 1153 manages power received wirelessly or wiredly and powerapplied to each component of the wireless power receiver 1150. The AP1152 receives power information from the PMIC 1153 and controls thecommunication unit 1151 to transmit a PRU dynamic signal for reportingthe power information.

A node 1156 connected to the WPIC 1154 is also connected to the TA 1158.If a wired charging connector is inserted into the TA 1158, apredetermined voltage, for example, 5V, may be applied to the node 1156.The WPIC 1154 determines whether the wired charging adaptor has beeninserted by monitoring a voltage applied to the node 1156.

The AP 1152 has a stack of a predetermined communication scheme, forexample, a WiFi/BT/BLE stack. Accordingly, for communication forwireless charging, the communication unit 1151 loads the stack from theAP 1152 and then communicates with the communication unit 1110 of thewireless power transmitter 1100, based on the stack, by BIBLE.

However, it may occur that data for wireless power transmission cannotbe retrieved from the AP 1152 due to power-off of the AP 1152 or thereis insufficient power to maintain an ON state of the AP 1152 duringretrieval of the data from a memory of the AP 1152 and usage of theretrieved data.

If the residual power amount of the battery 1159 is below a minimumpower limit as described above, the AP 1152 is turned off and thebattery 1159 is wirelessly charged using some components for wirelesscharging in the wireless power receiver 1150, for example, thecommunication unit 1151, the WPIC 1154, and the resonator 1155. A statein which power sufficient to turn on the AP 1152 cannot be supplied maybe referred to as a dead battery state.

Because the AP 1152 is not operated in the dead battery state, thecommunication unit 1151 may not receive the stack of the predeterminedcommunication scheme, for example, the WiFi/BT/BLE stack from the AP1152. In anticipation of this case, a part of the stack of thepredetermined communication scheme, for example, a BLE stack, is fetchedfrom the AP 1152 and stored in a memory 1162 of the communication unit1151. Accordingly, the communication unit 1151 may communicate with thewireless power transmitter 1100 using the stack of the communicationscheme stored in the memory 1162, that is, a wireless charging protocol,for wireless charging. The communication unit 1151 may have an internalmemory. The BLE stack may be stored in a Read Only Memory (ROM) in theSA mode.

As described above, a mode in which the communication unit 1151communicates using the stack of the communication scheme stored in thememory 1162 may be referred to as the SA mode. Accordingly, thecommunication unit 1151 may manage the charging procedure based on theBLE stack.

With reference to FIGS. 2 to 11, the concept of the wireless chargingsystem applicable to the embodiments of the present invention has beendescribed above. Below, methods for preventing occurrence of anabnormality according to embodiments of the present invention aredescribed in detail with reference to FIGS. 12 to 15.

FIG. 12 is a flowchart illustrating an operation for preventing anabnormality during wireless charging according to an embodiment of thepresent invention.

According to an embodiment of the present invention, a single wirelesspower transmitter transmits charging power to a plurality of wirelesspower receivers. When the wireless power transmitter supplies chargingpower to the plurality of wireless power receivers, various algorithmsmay be used to determine transmission power of the wireless powertransmitter, because the plurality of wireless power receivers maydiffer in terms of characteristics, states, and types.

For example, a minimum error (Vrect_setmin_error) tracking algorithm ora minimum power efficiency tracking algorithm is available toresonance-based wireless charging.

The minimum error tracking algorithm selects a wireless power receiver(that is, a PRU) having a highest power usage rate as a dominantwireless power receiver and controls a transmission power level of awireless power transmitter (that is, a PTU) so that the differencebetween a Vrect value of the dominant wireless power receiver and aVrect_set value indicated by a PRU static parameter may be minimized.The transmission power level of the wireless power transmitter may becontrolled by controlling current Itx flowing through a coil.

The minimum power efficiency tracking algorithm controls a transmissionpower level of a wireless power transmitter to achieve a maximumefficiency by calculating a ratio between the sum of power consumed by aplurality of wireless power receivers and power supplied by the wirelesspower transmitter. The transmission power level of the wireless powertransmitter may be controlled by controlling current Itx flowing througha coil.

Referring to FIG. 12, a wireless power transmitter (PTU) transmitswireless charging power to a plurality of wireless power receivers(PRUs) based on a power value determined according to a first mode (forexample, a mode corresponding to the minimum error tracking algorithm)in step S1201.

If an abnormality (for example, over voltage, over current, or overtemperature) is expected to occur in the wireless power transmitter or awireless power receiver and thus a predetermined abnormality occurrencecondition is satisfied during transmission of power from the wirelesspower transmitter to the plurality of wireless power receivers (forexample, a predetermined threshold or a threshold range in which asystem error occurs is reached) in step S1203, the wireless powertransmitter switches from the first mode (for example, the modecorresponding to the minimum error tracking algorithm) to a second mode(for example, a mode corresponding to the minimum power efficiencytracking algorithm) in step S1205.

Therefore, the wireless power transmitter transmits wireless chargingpower to the plurality of wireless power receivers based on a powervalue determined according to the second mode in step S1207.

According to an embodiment of the present invention, if the abnormalitysuch as over current, over voltage, or over temperature is overcomeduring power transmission in the second mode and thus a predeterminedabnormality release condition is satisfied during power transmission inthe second mode in step S1209, the wireless power transmitter switchesfrom the second mode (for example, the mode corresponding to the minimumpower efficiency tracking algorithm) to the first mode (for example, themode corresponding to the minimum error tracking algorithm) in stepS1211.

Therefore, the wireless power transmitter transmits wireless chargingpower to the plurality of wireless power receivers based on a powervalue determined according to the first mode in step S1213.

For example, if the wireless power transmitter approaches a threshold atwhich occurrence of a system error (for example, over voltage, overcurrent, or over temperature) is expected and thus each measurementfalls within a predetermined range during operating in the modecorresponding to the minimum error tracking algorithm, the wirelesspower transmitter operates in the minimum power efficiency trackingalgorithm by switching to the mode corresponding to the minimum powerefficiency tracking algorithm.

When the operation mode is switched as described above, the differencebetween a Vrect value of a dominant wireless power receiver determinedby the minimum error tracking algorithm and a predetermined Vrect_setvalue may become broad, thereby decreasing the efficiency of thedominant wireless power receiver. However, as the efficiencies of theother wireless power receivers being charged increase, total efficiencymay increase. Since Vrect values of the other wireless power receiversapproach their Vrect_set values, the resulting increase in theirefficiencies may lead to a decrease in voltage, current, or temperature,thereby preventing an occurrence of the abnormality.

If the system or a device is stabilized in this manner, the wirelesspower transmitter may switch from the mode corresponding to the minimumpower efficiency tracking algorithm to the mode corresponding to theminimum error tracking algorithm.

FIG. 13 is a flowchart illustrating an operation for preventing anabnormality during wireless charging according to an embodiment of thepresent invention.

Referring to FIG. 13, a wireless power transmitter determines atransmission power value, taking into account a dominant wireless powerreceiver among a plurality of wireless power receivers in step S1301.The wireless power transmitter transmits wireless charging power to theplurality of wireless power receivers based on the determined powervalue in step S1303.

If an abnormality (for example, over voltage, over current, or overtemperature) is expected to occur in the wireless power transmitter or awireless power receiver and thus a predetermined abnormality occurrencecondition is satisfied during transmission of power from the wirelesspower transmitter to the plurality of wireless power receivers (forexample, a predetermined threshold or a threshold range in which asystem error occurs is reached) in step S1305, the wireless powertransmitter sets a wireless power receiver corresponding to theabnormality occurrence condition as the dominant wireless power receiverin step S1307.

The wireless power transmitter determines a transmission power value,taking into account the changed dominant wireless power receiver, instep S1309. The wireless power transmitter transmits wireless chargingpower to the plurality of wireless power receivers using the determinedpower value in step S1311.

According to an embodiment of the present invention, if the abnormalitysuch as over current, over voltage, or over temperature is overcome andthus a predetermined abnormality release condition is satisfied duringpower transmission in consideration of the changed dominant wirelesspower receiver in step S1313, the wireless power transmitter resets theinitial dominant wireless power receiver as a current dominant wirelesspower receiver in step S1315. The wireless power transmitter determinesa transmission power value, taking into account the reset dominantwireless power receiver (that is, the initial dominant wireless powerreceiver), in step S1316, and transmits wireless charging power to theplurality of wireless power receivers using the determined transmissionpower value in step S1317.

According to an embodiment of the present invention, for example, if thewireless power transmitter determines transmission power according tothe mode corresponding to the minimum error tracking algorithm, thewireless power transmitter selects a wireless power receiver having ahigh power usage rate as a dominant wireless power receiver from among aplurality of wireless power receivers and controls the transmissionpower in such a manner that a Vrect value of the dominant wireless powerreceiver approaches a Vrect_set value.

Since the minimum error tracking algorithm is designed so that a Vrectvalue of a specific wireless power receiver (for example, a dominantwireless power receiver) may track a Vrect_set value of the wirelesspower receiver, a Vrect value of at least one other wireless powerreceiver may diverge from a Vrect_set value of the wireless powerreceiver, in multi-charging. For this reason, a voltage, current, ortemperature of the at least one other wireless power receiver may reachan error threshold.

For example, the above abnormal situation may occur more frequently inthe following multi-charging cases in which:

1. a wireless power receiver coupled well to a wireless powertransmitter and a wireless power receiver coupled poorly to the wirelesspower transmitter are charged at the same time;

2. the difference between the capacities of resonators in wireless powerreceivers is great; and

3. the difference between power classes (for example, categories) ofwireless power receivers is great.

If such an abnormality occurs during multi-charging, the wireless powertransmitter selects a wireless power receiver that approaches an OverVoltage Protection (OVP), Over Current Protection (OCP), or OverTemperature Protection (OTP) threshold as a dominant wireless powerreceiver from among a plurality of wireless power receivers, because thewireless power transmitter is monitoring charged states of the wirelesspower receivers. Accordingly, as the dominant wireless power receiverreaches an optimum operating range by making a Vrect value of thedominant wireless power receiver close to a Vrect_set value, the errorsituation may not occur.

If a Vrect of any other wireless power receiver reaches or falls below aVrect_min value, charging of the wireless power receiver isdiscontinued. Therefore, even though the Vrect value of the dominantwireless power receiver does not reach the Vrect_set value, tracking isstopped at a point where the Vrect value of any other wireless powerreceiver is not below the Vrect_min value. In spite of the discontinuedtracking, the probability of reaching an error situation may be reduced,because the wireless power transmitter has reduced Itx with respect tothe transmitted power.

If the wireless power receiver close to an error situation is stabilizedin this manner, the wireless power transmitter rests the wireless powerreceiver having the highest power usage rate in the original algorithmas a dominant wireless power receiver.

FIG. 14 is a flowchart illustrating an operation for preventing anabnormality during wireless charging according to an embodiment of thepresent invention.

Referring to FIG. 14, a wireless power transmitter transmits wirelesscharging power to a plurality of wireless power receivers in step S1401.

Upon sensing an occurrence of an abnormality (for example, over voltage,over current, or over temperature) in at least one wireless powerreceiver during power transmission to the plurality of wireless powerreceivers in step S1402, the wireless power transmitter transmits apower adjust command to the at least one wireless power receiver in stepS1403.

According to an embodiment of the present invention, for example, thewireless power transmitter commands the wireless power receiver toreduce load current of the wireless power receiver by transmitting apower adjust command in a PRU control parameter as illustrated in Table5 and Table 6 below.

TABLE 5 Field Octet Description Use Units Enables 1 PTU turn on. PTCMandatory N/A on indication etc. Permission 1 PRU is permitted inMandatory N/A PTU. Time Set 1 PTU sets up time. Mandatory ms RFU 2Undefined N/A N/A

TABLE 6 7 6 5 4 3 2 1 0 Enable PRU Enable PRU Adjust power command RFURFU RFU RFU output charge indicator 1 = Enable 1 = Enable 00 = Maximumpower RFU RFU RFU RFU 0 = Disable 0 = Disable 01 = 66% * P_(RECT) _(—)_(MAX) 10 = 33% * P_(RECT) _(—) _(MAX) 11 = 2.5 W

If the wireless power receiver is capable of reducing its load current,the wireless power receiver reduces power consumption so that thewireless power transmitter may have extra power to charge anotherwireless power receiver or the wireless power receiver drops itscurrent, voltage, or temperature.

If a current value Itx of power supplied by the wireless powertransmitter is excessive during charging a plurality of wireless powerreceivers, it is highly probable that a wireless power receiver willface an error situation (e.g., over voltage, over current, or overtemperature).

According to an embodiment of the present invention as described above,if the wireless power transmitter senses a wireless power receiver thatmay face an abnormal situation, that is, the wireless power receiverapproaches an error threshold set for determining an error occurrence,the wireless power transmitter commands the wireless power receiver toreduce power required for the load of the wireless power receiver.According to an embodiment of the present invention, if the wirelesspower receiver is capable of power rationing, the wireless powerreceiver drops a voltage or current flowing in it or its temperature byreducing the power of its load.

FIG. 15 is a flowchart illustrating an operation for preventing anabnormality during wireless charging according to an embodiment of thepresent invention.

Referring to FIG. 15, a wireless power transmitter transmits wirelesscharging power to a plurality of wireless power receivers in step S1501.

Upon sensing an occurrence of an abnormality (for example, over voltage,over current, or over temperature) in at least one wireless powerreceiver during power transmission to the plurality of wireless powerreceivers in step S1503, the wireless power transmitter transmits apower reception stop command to the at least one wireless power receiverin step S1505.

According to an embodiment of the present invention, the wireless powertransmitter commands the wireless power receiver to discontinue powerreception by transmitting a power reception stop command in a PRUcontrol parameter so that the wireless power receiver discontinuesreception of power required for charging.

As the wireless power receiver discontinues power reception, thewireless power transmitter may have extra power to charge anotherwireless power receiver or the wireless power receiver may drop itscurrent, voltage, or temperature.

As is apparent from the foregoing description, according to anembodiment of the present invention, since a wireless power transmitterexpects various abnormalities that may occur during transmission ofcharging power to a plurality of wireless power receivers andappropriately handles the expected occurrences of abnormalities, theabnormalities can be effectively prevented.

According to an embodiment of the present invention, if the wirelesspower transmitter expects an occurrence of an abnormality in at leastone wireless power receiver, the wireless power transmitter can preventthe abnormality by changing or modifying a charging algorithm.

According to an embodiment of the present invention, if the wirelesspower transmitter expects an occurrence of an abnormality in at leastone wireless power receiver, the wireless power transmitter can preventthe abnormality by changing a dominant wireless power receiver.

According to an embodiment of the present invention, if the wirelesspower transmitter senses an occurrence of an abnormality in at least onewireless power receiver, the wireless power transmitter can prevent theabnormality by transmitting a power adjust command to the at least onewireless power receiver.

According to an embodiment of the present invention, if the wirelesspower transmitter senses an occurrence of an abnormality in at least onewireless power receiver, the wireless power transmitter can prevent theabnormality by transmitting a power reception stop command to the atleast one wireless power receiver.

While the present invention has been shown and described with referenceto certain embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the scope and spirit of the present invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A control method of a wireless power transmitter, the method comprising: transmitting power to a plurality of wireless power receivers based on first power information of a first wireless power receiver from among the plurality of wireless power receivers; selecting, before reaching a fault condition that requires power to be shut down in the wireless power transmitter, a second wireless power receiver from among the plurality of wireless power receivers; and in response to the second wireless power receiver being selected, transmitting power to the plurality of wireless power receivers based on second power information of the second wireless power receiver, wherein the fault condition comprises at least one of an over-temperature error, an over-current error, and an over-voltage error.
 2. The method of claim 1, further comprising: transmitting a power adjust command to reduce the power to a lower percentage of a maximum received power level.
 3. The method of claim 1, wherein the over-voltage error is based on a measured voltage value exceeding a predetermined voltage value, the over-current error is based on a measured current value exceeding a predetermined current value, and the over-temperature error is based on a measured temperature value exceeding a predetermined temperature value.
 4. The method of claim 2, wherein the power adjust command is a control command for reducing power consumption of at least one wireless power receiver from among the plurality of wireless power receivers.
 5. The method of claim 2, wherein the power adjust command is included in a power receiving unit control signal.
 6. The method of claim 1, further comprising: measuring at least one value of a voltage value, a current value, and a temperature value in the wireless power transmitter; and determining that the power of the wireless power is shut down when the at least one value of the measured voltage value, the measured current value, and the measured temperature value falls within a predetermined range indicating that the at least one value approaches the fault condition set for determining whether power of the wireless power transmitter is shut down.
 7. A wireless power transmitter for wirelessly charging a plurality of wireless power receivers, the wireless power transmitter comprising: a power transmitter configured to wirelessly transmit power to the plurality of wireless power receivers based on a first power information of a first wireless power receiver; a communication unit configured to transmit a signal to the plurality of wireless power receivers; and a controller configured to: select, before reaching a fault condition that requires power to be shut down in the wireless power transmitter, a second wireless power receiver from among the plurality of wireless power receivers; and in response to the second wireless power receiver being selected, control the power transmitter to transmit power to the plurality of wireless power receivers based on a second power information of the second wireless power receiver, wherein the fault condition comprises at least one of an over-temperature error, an over-current error, and an over-voltage error.
 8. The wireless power transmitter of claim 7, wherein the controller is further configured to transmit a power adjust command to reduce the power to a lower percentage of a maximum received power level.
 9. The wireless power transmitter of claim 7, wherein the over-voltage error is based on a measured voltage value exceeding a predetermined voltage value, the over-current error is based on a measured current value exceeding a predetermined current value, and the over-temperature error is based on a measured temperature value exceeding a predetermined temperature value.
 10. The wireless power transmitter of claim 8, wherein the power adjust command is a control command for reducing power consumption of at least one wireless power receiver from among the plurality of wireless power receivers.
 11. The wireless power transmitter of claim 8, wherein the power adjust command is included in a power receiving unit control signal.
 12. The wireless power transmitter of claim 7, wherein the controller is further configured to: control to measure at least one value of a voltage value, a current value, and a temperature value in the wireless power transmitter; and determine that the power of the wireless power transmitter is shut down when the at least one value of the measured voltage value, the measured current value, and the measured temperature value falls within a predetermined range indicating that the measured at least one value approaches the fault condition set for determining whether the power of the wireless power transmitter is hut down.
 13. The method of claim 1, wherein the wireless power transmitter enters a fault state if the wireless power transmitter reaches the fault condition.
 14. The wireless power transmitter of claim 7, wherein the wireless power transmitter enters a fault state if the wireless power transmitter reaches the fault condition. 